Conventional electric motors generally comprise of a cylindrical stator and a rotor assembly located within the stator. Typically, the rotor assembly is constructed with the aid of a heavy steel hub. The hub is used to ensure that the rotor laminations are connected to external structures and support the structure of the rotor assembly. The use of a hub requires special machining for locking rotor components or tabs to the hub. In the use of a hub to assemble the rotor assembly, the rotor components or tabs must be perfectly aligned to complete the assembly process.
In order for the hub to slide over the rotor lamination stack, a gap must be created. The hub is ordinarily contracted with the use of liquid nitrogen at −300° F. while the rotor laminations are expanded with the use of an oven at 400° F. As the temperatures normalize, the gap dissipates and a “shrink-fit” between the hub and rotor laminations results.
Other typical rotor assemblies include a supporting rotor shaft extending through a central hole in the stack of rotor laminations. The rotor shaft may also be welded onto either end of the stack of rotor laminations.